1) Field of the Invention
The present invention relates to an organic dispersion-type electroluminescence device (hereinafter called "EL device"), and particularly to an EL device capable of providing a long life.
2) Description of the Related Art
In conventional organic dispersion-type EL devices, those formed by dispersing fluorescent powder such as ZnS(Cu) into a polymer matrix have been used as a luminescent layer. The polymer matrix, uses a high dielectric constant polymer, such as cyanoethylated cellulose, cyanoethylated poly(vinyl alcohol), etc.
However, the polymer such as the above 2-cyanoethylated poly(vinyl alcohol) is produced by a method in which acrylonitrile is allowed to react with poly(vinyl alcohol) in the form of a Michel-type addition reaction under the presence of a basic catalyst and introducing 2-cyanoethyl groups into hydroxyl groups of poly(vinyl alcohol). Therefore, the hydroxyl groups of 10% or so are left in its repeating structure without being subjected to substitution, thereby increasing hygroscopicity due to the remaining of the hydroxyl groups.
Thus, such a luminescent layer as referred to above also has high hygroscopic capability, and the fluorescent powder in the luminescent layer is decomposed by hygroscopic water content depending upon variations with time, thus causing inconvenience such as a limitation on the luminescent life of each EL device.